Diaphragm spider



Nov. 5, 1935.

R. E. TOLERTON DIAPHRAGM SPIDER Filed Jan. 18, 1935 iAfi-mla m INVENTOR. FAY E 75LERTo/v.

I ATTORNEY Patented Nov. 5, 1935 UNITED I STATES PAT ENT OFF I QE DIAPHRAGM SPIDER Ray E. Toler'ton, Fort Wayne, Ind assigiiorto" The Magnav'o'x Goinpany,-Fort-Wayne; hide, a

corporation of Arizona In mounting diaphragmsoi the conical type,

such as are now almost exclusively; used on electro-dynamic loud speakers, it is the practice to secure the rim of the diaphragm by means of a flexible flange to a fixed annular support and to center the small end of the diaphragm and its driving coil concentric with the magnetic field air gap by means of a so-calledcentering spider which is either permanently or adjustably secured to asuitable support. This centering spider has taken a great; many forms but the most common type is that inwhich a flat member of relatively sti-ffmaterial, having outwardly extending flexible arms, is secured transversely to the axis of the diaphragm and coil" and: fixed at its outer extremities to a supporting means carried' by the field structure.

With a diaphragm mounting of the above character it is important, both from the acoustical I also important that the material be such that its flexibility will not be effected by changes in temperature and/or humidity.

Centering spiders of the above character have been formed of a number of different materials such as fibre, hardrubber and various phenolic condensate products which are sold under the trade name Bakelite.

The above materials are available in sheet form and at the present time it is customary to cut the spiders from this sheet like material with a punch and die having the configuration of the centering spider desired. After the centering spider is thus punched from the sheet it is slipped over a cylindrical coil supporting spool and glued in place with its inner edge engaging the spool adjacent the point where the diaphragm is attached.

This-method of attaching the centering spider to the coil supporting spool has proven satisfactory where the spool is made of rigid material but when the spool is made in accordance with the more recent practice, i. e. of a single or twoply strip of paper, it has been found that the spider tends to flex along its point of engagement with the spool and thus break the bond formed by gluing the spider to the spool.

In order to overcome the above difiiculty and form abetter glued connection between the centering spider and the coil' supporting spool, I provide areinforcing flangeabout the inner edge of the centering spider which will stiffen the spider and-prevent a flexing at this point. This arrangement also produces an elongated surface 1- to which the coil spool may be glued.

The most desirable material now available for this type of spider is manufactured by the hot press method and consequently it is impossible to form a flange thereupon after the material has cooled without breaking same. Therefore, in order to overcome this difficulty and make possible the use of this material, as contemplated by my invention, I propose to form a flange upon the sheet material while it is hot and plastic, as during its process of manufacture, and then punch the spider therefrom after the material has hardened. v A

For a better und'erstanding of my invention reference should be had to the accompanying drawing, wherein I have shown by way of illustration and not ofli'mit'ation a preferred embodiment thereof.

4 in the drawing, wherein like numerals refer to like parts" throughout the several views;

Figural is a plan view of'a centering spider attached to a coil supporting. spool,

Figure 2 is a sectional view taken along line IIf-TI of Figure 1, showing the position of' the diaphragm by dot and dash lines,

Figure 31s airaginentary sectional view taken along line III -II I of Figure 1', looking in the directionof arrows, and

Figure 4 is a fragmentary perspective view showing a sheet of spider material as formed prior to the punching of' the spiders therefrom, and

Fig. 5 is an enlargedfragmentary view in section showing a preferred form of spider material.

As shown in-Figurel of the drawing, the particular spider selectedby me for illustration comprises a thinflat member having acentral annular portion ID from which oppositely disposed outwardly extending-arms l I project. The arms H are shown as curved inwardly toward. each other where they merge and terminate to' form support engaging portions l2 on-opposite sides of the annular portion l0- The spider is also shown as-having a pair of: ears l3 which project. from one side of the annular portion Iii. The function of these ears I3 is to be described in more detail hereinafter. The annular portion IU' of 5 the centering spider is also illustrated as having an upwardly projecting flange [4 within which there is secured a suitable coil supporting spool I5.

As illustrated in Figure 2 of the drawing, the coil supporting spool [5 has a recess [6 in which a coil or winding l! is disposed. The ends of the winding I1, designated by the numeral 3, project through the spool l5 adjacent one end of the recess I6 and are then passed out through slits 19 formed in the end of the spool I5 where they are secured to the ears l3, as will be hereinafter described.

In this figure of the drawing the flange I4 of the spider is shown as disposed about the upper end of the coil supporting spool l5 and over the slits [9 so that the ends l8 of the winding i! are located below the spider at a point where they will not interfere with the attachment of the spider or the diaphragm 20 to the coil supporting spool l5.

By referring to Figure 3 of the drawing it will be noted that the ends of the winding I! pass through small holes 2| and along the inside of the spool [5 to the point where they pass out through the slits l9 to a position below the previously referred to ears [3. After the ends it of the winding I! have been thus brought out below the spider, they are then laced through perforations 22 formed in the ears l3 and twisted about and soldered to suitable flexible lead-out wires 23 which connect with an external circuit, such as the output of a radio receiver or other source of modulated current. The lacing of the ends of the winding l'l through the ears i3 and about the flexible lead-out wires 23, in addition to affording a good electrical connection therebetween, also serves to secure the ends of the winding [1 and the lead-out wires 23 to the moving elements in a simple, inexpensive and eifective manner.

For maximum electrical and acoustical efficiency it is necessary that the winding ll be disposed in an air gap which is as narrow as it is mechanically practical to provide and also that the winding l1 and its supporting spool l5 be made as light as possible. Therefore, since the size of the wire used in forming the winding I! must be of a definite diameter and comprise a definite number of turns it has been found necessary, in order to meet the above requirements, to construct the supporting spool l5 of comparatively thin material which in most cases comprises a single or double layer of paper or paper and silk pressed with a suitable plastic into the shape desired.

This type of spool, due to its thin construction, is not very rigid and as a result it is impractical to secure the centering spider thereto with an edgewise engagement as has been the practice in the past. The principal diflicuty in this connection is due to this lack of rigidity in the coil supporting spool I5. When the spool I5 is of rigid construction it serves to stiffen the spider at the point of attachment but where the spool lacks rigidity the inner annular portion ID of the spider which engages the spool will flex and break the glued connection and thereby destroy its function. However, by reinforcing the annular portion ill of the spider with a flange [4, as suggested above, the flexing of the spider is limited to points remote from its spool engaging portion and as a result it is possible to construct the spool l5 of extremity thin material. At the same time the inner surface of the flange 14 will provide an excellent surface to which the spool I5 can be glued.

The most practical method of forming such a centering spider is to punch it from sheet material after the material has cooled and taken a definite character. When the spider is punched from a flat sheet of material by this method it will be impossible to form any flange thereupon as the material will break unless it can be rendered plastic by the application of a liquid solvent or heat. A material of this type, however, is impractical as its characteristics will not remain constant under changing humidity and temperature conditions. For best results it is necessary to form the spider of a material which is impervious to moisture and unaffected by all normal operating temperature changes.

A further disadvantage in forming a flange upon the spider, as suggested above, after it has been cut to the particular shape desired, is that the whole spider structure will be distorted when heat or a solvent is applied thereto for the purpose of rendering it plastic.

The best material for spiders of the character contemplated, known to me at the present time,

is a Woven fabric treated with a phenolic condensate product which is baked under pressure until it has taken a permanent set. This material, however, can not be reformed after it has been produced by the above process and therefore, in order to provide a reinforcing flange upon a spider of this material, I propose to deform the sheet and thus provide for the flange when the material is in its original plastic condition.

In accordance with this latter aspect of my invention, I provide the sheet from which the spider is to be struck with depressed or raised portions which correspond in diameter and length to the diameter and length of the flange desired upon the spider.

As illustrated in Figure 4 of the drawing the sheet material, designated by the numeral 24, is

provided with a plurality of depressed portions 25 which are so spaced that the spiders may be punched from the sheet about the depressions.

With such a sheet the spiders can be punched therefrom in the same manner as has been the practice in the past. When this material is used the central punch will be modified to have a diameter corresponding to the inner diameter of the depressions 25 and the punching die will be modified to accommodate one of the depressions 25.

After the punch and die have been designed, as suggested above, the operator need only align a depression 25 properly in the die and proceed as with the ordinary punching operation. The result will then be a flat spider having a reinforcing flange thereupon.

When the sheet material 24 is formed of a fabric saturated with a phenolic condensate product the fabric can be disposed between a pair of pressing dies and there shaped as illustrated in Figure 4. of the drawing, and when the sheet is formed without the fabric the plastitc material can be spread between the forming dies in any suitable manner and then pressed to the desired thickness.

In Figure 5 of the drawing the centering spider is shown formed of a fabric 26 impregnated with the phenolic condensate product, as described above. The construction of a spider of this material results in a member of phenolic condensate having a woven fabric imbedded therein throughout its entire area. When the spider is formed in this manner it can, due to the reinforcing characteristic of the fabric 26, be made considerably thinner than is possible when the fabric is omitted and at the same time the presence of the fabric does not interfere with the pressing and/ or punching operations.

By my improved method of procedure it is possible to retain all of the desirable features obtained by punching the spiders from cold sheet material, such as uniformity of product, ease of manufacture, andlow cost, and at the same time provide spiders having all of the improved characteristics enumerated above.

While I have, for the sake of clearness and in order to disclose my invention so that the same can be readily understood, described and illustrated a specific device and arrangement, I desire to have it understood that this invention is not limited to the specific means disclosed but may be embodied in other ways that will suggest themselves, in view of this disclosure, to persons skilled in the art. It is believed that this invention is new and it is desired to claim it as such so that all such changes which come within the scope of the appended claims are tobe considered as part of this invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. In a loud speaker diaphragm assembly, the combination of a conical diaphragm, a cylindrical coil supporting member disposed at the apex thereof having an exterior recess for a coil, said coil supporting member also having slits in its end remote from said exterior recess into which the ends of the coil are disposed, a driving coil wound in said recess, the ends of said coil extending through and along the interior of the coil supporting member to a point where they are brought out through said slits in the end of said coil supporting member, a transversely extending flexible centering support disposed about the end of said coil supporting member and over said slits to retain the ends of the coil therein, and means upon said centering support to which the ends of said coil and suitable lead out wires can be anchored.

2. In a loud speaker diaphragm assembly, the combination of a cylindrical coil supporting member having slits in one end thereof and a peripheral coil positioning recess at the other end thereof, said coil supporting member also having holes 5 adjacent one end of said coil positioning recess in alignment with said slits, a coil of wire wound in said recess, the ends of said coil of wire being passed in through the holes in said coil supporting member and brought out through said slits, 10 and a transversely extending flexible support having a cylindrical flange disposed over the end of said coil supporting member for closing said slits and reinforcing said coil supporting member.

3. A coil centering support for electrodynamic l5 loud speakers, comprising a transversely disposed flat member of hot pressed phenolic condensate material having portions adapted to engage stationary supports and a central annular portion for engaging a cylindrical coil support, 20 the central annular portion of said flat member having a circular opening therethrough into which said coil support is disposed, a continuouscylindrical flange extending completely around the circular opening in said central annular por- 25 tion forming a bearing for the cylindrical coil support, and .a continuous sheet of fabric imbedded in said phenolic condensate material and extending throughout said flat member and said cylindrical flange.

4. A coil centering support for an electrodynamic loud speaker diaphragm, comprising a cylindrical coil supporting member, a transversely extending member of hot pressed phenolic condensate having a flat annular central portion 85 from which outwardly extending flexible arms project, a cylindrical flange formed about the inner edge of said flat annular central portion to which said coil supporting member is attached for preventing a flexing of the flat annular cen- 40 tral portion when said arms are flexed by movement of the diaphragm, and a woven fabric imbedded in said hot pressed phenolic condensate and extending throughout the flat transversely extending member and the cylindrical flange at the inner edge thereof.

RAY E. TOLERTON. 

